This method statement is applicable for collecting samples for concrete before and during concrete pouring activities and doing the standard tests.
- BS 1881Part 5, Methods of Testing Hardened Concrete for Other Than Strength
- BS EN 12350-1: 2000, Methods of Sampling Fresh Concrete
- BS EN 12350-2: 2000, Methods of Testing Fresh Concrete.
- BS EN 12350-6: 2000 Part 108 to Part 113 Part 124, Method for Determination of Density of Compacted Fresh Air Methods of Making & Curing Test Specimens Analysis of Hardened Concrete.
- BS EN 196, Methods of Testing Cement
- ASTM C 94/BS 5328, Ready Mixed Concrete
- Concrete Mixers
- Slump measurement cone and equipments
- Concrete cube moulds for concrete sampling
- Meter tape
- Curing pool
- Cube crushing and testing equipment
- Equipment for Durability test and moisture content
- Safety Equipment As applicable
Concrete Sampling Procedure
- Sample shall be taken for each class of concrete in production at each plant for use for a project.
- Samples of concrete shall be taken at the point of mixing or of deposition as instructed by the consultant.
- All samples shall be taken in the presence of a representative from the contractor/consultant/client as applicable in accordance with the sampling procedures described in BS EN 12350-1:2000 (Testing fresh concrete).
- Samples shall be taken on the basis of one for each 20 cubic meter of concrete placed or more often dependent on concrete grade and location as agreed. In any case not less than one sample per day or one sample for each pour of concrete placed shall be taken, whichever is the more frequent.
- From each sample 6 x 150mm cubes shall be casted, cured and tested as set out in BS EN 12390-1:2000.
- When the concrete contains aggregate with a nominal size of 75mm, all aggregate retained on a 50mm sieve shall be removed before casting cubes or making slump measurements. Six 200mm test cubes shall be casted from each sample and cured as set out in BS EN 12390-1:2000 [Testing hardened concrete, Shape, dimensions and other requirements for specimens and moulds]. In this instance, samples shall be taken on the basis of one for each 100 cubic meter of concrete placed but in any case not less than one sample per day or one sample for each pour of concrete placed, whichever is the more frequent.
Testing Of Concrete
For all classes of concrete in production three cubes shall be tested at 7 days and three at 28 days or as required by the consultant/client.
The average strength of the three cubes crushed at & or 28 days shall be referred to as one test result.
Concrete shall be deemed to comply with the strength specified if:
Any one test result is not less than 85% of the final trial mix strength for that class of concrete.
The average of any 6 successive test results for the same class of concrete is not less than 90% of the final trial mix strength for that class.
No single cube result is less than 75% of the final trial mix strength for that class of concrete.
All the tests shall be conducted by an approved testing agency which should have previous track record for doing the concrete testing.
The slump or compacting factor of the concrete shall be determined for each batch from which samples are taken and in addition for other batches at the frequency agreed between all parties
The slump of each sample shall be carried out in accordance with BS EN 12350-2:2000 at the time of sampling.
Concrete may only be accepted for placement if its workability is within one of the following limits at the time of placement:
- The slump of the concrete in any batch shall not differ from the value established by the trial mixes by more than 25mm or one third of the value, whichever is the greater.
- The variation in value of the compacting factor, if used in place of a slump value, shall be within the following limits:
For value of 0.9 or more ±0.03
For value between 0.8 and 0.9 ±0.04
For values of 0.8 or less ±0.05
Water/ Cement Ratio:
The water/cement ratio as estimated from the results of slump test section as above, or when required by the client, determined by samples from any batch shall not vary by more than 5% from the specified maximum value or the value established during the trial mixes, whichever is the lower.
Air Content Testing
The percentage air content determined from individual samples taken at the point of placing the concrete and representative of any given batch of concrete shall be within +1.5% of the specified value. The average percentage air content from any four consecutive determinations from separate batches shall be within +1.0% of the specified value.
The air content shall be checked for each batch.
Total air content comprises entrained air plus entrapped air remaining after compaction.
Temperature Monitoring of Concrete
For each sample the temperature of the fresh concrete shall be measured and frequency of measurement shall depend on contractor/client requirements.
Samples of concrete shall be tested for durability properties by undertaking absorption and permeability tests as mentioned hereunder and shall coincide with samples taken from cube strength tests as appropriate.
Chloride Permeability: As per AASHTO T277. The maximum charge pass at 28 days shall be 3500 for normal concrete or 1500 for GGBS concrete. For other types respective standard can be referred.
Water Permeability to DIN 1048: The maximum penetration at 28 days shall be 10mm for silica fume concrete and 15mm for general concrete.
Initial Surface Absorption: As per BS 1881-208:1996 [Testing concrete. Recommendations for the determination of the initial surface absorption of concrete] (ISAT). Maximum ISAT at 28 days (10 minute test) shall be 0.15ml/m2/sec for both silica fume concrete and for normal concrete.
30 Minute Absorption: BS 1881-122:1983 [Testing concrete. Method for determination of water absorption]. Maximum absorption shall be 1.5% at 21 days for silica fume concrete and 2.0% at 21 days for concrete generally.